There’s a strange whiff of mistrust in these British isles around the description “political novel”; it’s a term sometimes confused with polemic, and an absence of nuance and subtlety. Sunjeev Sahota’s second novel makes a nonsense of common assumptions about what it means to write a political novel.

His debut, Ours Are the Streets, looked into the mind of a would-be suicide bomber in Sheffield and won him a place on the 2013 Granta Best of Young British Novelists list. The new novel centres around the lives of three Indian men and one British-Indian woman. The three men – Tochi, Randeep and Avtar – live together with other migrant workers in a house in Sheffield; the woman, Narindar, is married to Randeep but barely knows, or wants to know, him and lives separately in a flat.

In the first half, the book alternates between shorter chapters about the four characters in Sheffield, and novella-length sections about each of them prior to their arrival there. It is a risky strategy – if just one of the sections sags by comparison with the others the whole structure could collapse – but Sahota is more than equal to the task. The first story is that of Tochi, a chamar or “untouchable” in an India of heightened Hindu nationalism where a man risks everything by merely being perceived as trying to break out of the strict rules of caste. Sahota is not, however, the kind of writer who will seize on instances of the most violent forms of bigotry – throughout the novel, his eye is drawn more frequently to the smaller moments of injustice that wear people down and also the acts of grace that they can barely believe possible.

Tochi’s story allows us to understand why he holds himself separate from the other men with whom he lives and works in Sheffield, and the following novella-length section bringing together the tales of Avtar and Randeep reveals why their relationship is caught somewhere between acquaintances and friends. Former neighbours, whose lives in the world of the middle class in India prove to be precarious, they are propelled, respectively, by love and shame to travel to England in search of work. The final story is that of Narindar, a devout British Sikh woman for whom goodness is at the heart of religious practice. But what does it mean to be good in an unjust world? What is a devoted daughter to do when her idea of what is moral runs counter to her family’s notions of honour? What is a law-abiding British woman to do when what she believes to be the path to virtue runs counter to the law? The question of the responsibilities borne by the citizens of the more fortunate nations of the world towards those from other countries is at the heart of Narindar’s story, but it is told in the most intimate of ways, as an issue that is not theorised but deeply felt. And the question remains open all the way to the end.

The second half of the novel moves forward, as the characters’ relationships with each other grow more tangled, and their situations more fraught. Tabloid phrases such as “scam marriages”, “illegal workers”, “abuse of student visas” are placed within the context of lives filled with love and desperation. Yet the book should not be read for its worthiness rather than for its literary qualities. Sahota is a writer who knows how to turn a phrase, how to light up a scene, how to make you stay up late at night to learn what happens next. This is a novel that takes on the largest questions and still shines in its smallest details – an encounter between a lonely old Englishman and the Indian boy from a call centre whom he befriends over the phone, never dreaming the boy might arrive at his doorstep; the misunderstanding of a woman who thinks a man is deliberately snubbing her when the reality is that he is unable to read the messages she leaves for him; the impossibility of friendship between young men who know there are too few scraps to go around and too many dependants relying on them to be the ones to grab hold of the scraps.

Through these stories and others, Sahota moves some of the most urgent political questions of the day away from rhetorical posturing and contested statistics into the realm of humanity. The Year of the Runaways is a brilliant and beautiful novel.

• To orderThe Year of the Runaways for £11.99 (RRP £14.99) go to bookshop.theguardian.com or call 0330 333 6846. Free UK p&p over £10, online orders only. Phone orders min p&p of £1.99. Kamila Shamsie’s A God in Every Stone is published by Bloomsbury.